Global GNSS Ionosphere Maps: GFZ

Global navigation satellite systems (GNSS) are primarily designed for providing positioning, navigation and timing services to the users. They are, however, also an effective tool to observe the Earth’s ionosphere and measure its total electron content (TEC) - the integrated electron density of the ionospheric plasma along the signal paths from the satellites to the receiver.

By combining the observations of a globally distributed network of ground receivers, a global model of the TEC can be derived. It provides valuable information for atmospheric and space weather studies and can be used to assess and mitigate the impact of the ionosphere on GNSS-based positioning services or high-precision geodetic solutions.

Based on a network of around 250 IGS GNSS tracking stations, we routinely generate global TEC maps using our EPOS.P8 GNSS analysis software. Observation data from GPS, GLONASS, and Galileo satellites are used. The examples in the figure show how the maximum TEC follows the direction of the sun, as the ionospheric plasma is mostly generated by solar radiation. Geomagnetic storms that occur more often during high solar activity can lead to very large TEC values. The globally averaged TEC serves as an ionospheric index, which for instance clearly shows the eleven year solar cycle.

[Translate to English:] Global TEC maps generated at GFZ for a day with moderate geomagnetic activity above (April 30, 2021) and the geomagnetic storm on St. Patrick's below (March 17, 2015) — Figure 1: Global TEC maps generated at GFZ during a day with moderate geomagnetic activity at the top (April 30, 2021) and the St. Patrick’s day geomagnetic storm at the bottom (March 17, 2015) *(Source: GFZ)*

[Translate to English:] Figure 2: Trend of the globally averaged TEC derived from the GFZ TEC maps, the F10.7 Index and the Ap Index; seasonal and annual effects as well as the 11-year solar cycle are clearly recognizable — Figure 2: Time series of mean vertical TEC extracted from the GFZ TEC maps, the F10.7 index, and the Ap index; seasonal and annual patterns as well as the 11 year solar cycle are visible *((Source: GFZ))*

Products

Brack A, Männel B, Bradke M, Brandt A, Nischan T (2021): GFZ Global Ionosphere Maps. V. 1.0. GFZ Data Services. https://doi.org/10.5880/GFZ.1.1.2021.006

Literature

Brack A, Männel B, Wickert J, Schuh H (2021): Operational Multi-GNSS Global Ionosphere Maps at GFZ Derived From Uncombined Code and Phase Observations. Radio Science 56(10):e2021RS007337. https://doi.org/10.1029/2021RS007337